Controllable electrical delay means



g- 21, 1951 J. w. TILEYI H 2,565,410

CONTROLLABLE ELECTRICKL DELAYMEANS Filed Sept. 20, 1944 2 Sheets-Sheet 1FIG. 1

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Aug. 21, 1951 J. w. TILEY 2,565,410

CONTROLLABLE ELECTRICAL DELAY MEANS Filed Sept. 20, 1944 2Sheets-Sheei'. 2

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32 35 MO DULATING 1 VOLTAGE soulzcz EWCITER Patented Aug. 21, 19512,565,410 CONTROLLABLE ELECTRICAL DELAY MEANS John W. Tiley,Philadelphia, Pa., Philco Corporation, Philadelphia,

ration of Pennsylvania Application September 20, 1944, Serial No.554,960 8 Claims. (Cl. 313-457) The present invention relates to spacedischarge apparatus and concerns particularly apparatus of the type inwhich an electric emission beam or electronic beam is produced.

An object of the invention is to provide improved methods and apparatusfor producing time delay effects.

Another object is to provide improved methods and apparatus forcontrolling delay of high frequency signals without employing filternetworks.

Another object is to provide arangements for producing the same absolutedelay for all ire. quency components of a signal.

Still another object is to provide arrangements for utilization or forcontrol of transit time effects.

An additional object of the invention is to provide means in electronbeam apparatus for lengthening the beam which may be utilized within agiven space.

Still another object of the invention is to provide transit timeapparatus in which the length of an electronic beam may be varied tovary time delay of the signal or for phase modulation.

Other objects of the invention are to provide means for varying thelength of an electronic beam spiral for varying the tightness or pitchof such a spiral and for varying the radius of such a spiral.

A further object of the invention is to provide means for multiplyingthe effective length of the path of a stream of electrons.

Other and further objects, features and advantages of the invention willbecome apparent as the description proceeds.

In carrying out the invention in one of the preferred embodimentsthereof, an evacuated tube or the like is provided having a concentricelectrode arrangement with a cathode at the center, a ring-shaped anodeand means for producing a magnetic field having a magnetic axissubstantially coaxial with the anode and the cathode of the tube.Suitable beam forming and focusing electrodes are provided so that,disregarding the magnetic field, an electronic beam or a plurality ofelectronic beams tends to leave the cathode and to travel radiallytoward the anode. As a result of the action of the magnetic field,however, the paths of the electrons are twisted or if a single beam isemployed, the electronic beam is twisted or coiled into a flat spiralform. Inasmuch as the beam forming and focusing electrodes impart aconstant velocity to the electrons, the transit time o! the assignor toPa., a corpoelectrons in traveling from the cathode to the anode orcollector is very greatly increased since the path has been lengthenedfrom a simple radius to a spiral, the number of convolutions of whichmay be made very great by selecting the magnetic field of suflicientstrength.

If an intensity controlling grid or control electrode is provided with asignal or carrier voltage applied thereto, the signal will be receivedby the collector anode with a time delay determined by the transit timeof the electrons.

Phase modulation of such a signal or carrier may be produced by varyingthe length of the electronic path, for example by varying the strengthof the beam-twisting magnetic field.

The path of an electron or the shape of an electronic beam is made totake the form of a spiral. The spiral may either be a flat one in asingle plane forming what is known as a pancake coil" or may take anyother spiral form desired such as along the surface of a cone or alongthe surface of a cylinder, for example, in the latter case forming whatis known as a helix or helical spiral.

The length of electron path and accordingly the transit time of theelectrons may be varied by varying the length of the spiral regardlessof the shape thereof. This may be done either by means of varyin thestrength of a beam twisting magnetic field as already mentioned or alsoby other means such as by a device for distorting the electron beam pathsuch as electrostatic deflection means, for example.

A better understanding of the invention will be ail'orded by thefollowing detailed description considered in conjunction with theaccompanying drawings, and its scope will be set forth in the claims.

In the drawing,

Fig. 1 is a schematic diagram of one embodiment of the inventionrepresenting an elevation with certain portions of the interior of theapparatus in section to leave other parts visible.

Fig. 2 is a view, looking from above, of a cross-section of theapparatus of Fig. l represented as cut by a plane 2-2 indicated in Fig.1.

Fig. 3 is a view corresponding to Fig. 1 illustrating an embodiment ofthe invention in which electrostatic beam deflection is employed formodulation purposes, and

Fig. 4 is a schematic diagram of an embodiment of the invention in whichthe electronic beam takes a helical or corkscrew form.

Like reference characters are utilized throughout the drawing todesignate like parts.

The apparatus forming an illustrative embodiment of the invention asillustrated in Figs. 1 and 2 comprises a relatively flat circularevacuated envelope assumed to be composed of glass for simplicity in theexplanation and illustration, containing electron emitting means such asa cathode l2 in the form of a cylinder at the center of the envelope II,and a ringshaped anode or collector l3 which is substantially coaxialwith the cathode l2. Suitable beam forming and focusing elements ofconventional form may be provided for confining the electron emission toa path along a plane substantially intersecting the envelopeperpendicular to its axis l4. Such electron directing and beam formingelements may take the form, for example, of a substantially tubularshield I5 surrounding the cathode l2 and having a radial opening It forprojecting a beam of electrons ll which will tend to move radiallyexcept for the means hereinafter to be described.

For controlling the intensity of the electron beam, that is the numberof electrons leaving the cathode |2 at a given time, a beam intensitycontrol grid l8 may be provided which surrounds the cathode I2 if noindividual beam is employed, or may merely be placed in front of theopening IS in the shield |5 if such an element is provided. If desired,a constant velocity grid I9 may also be provided, which is analogous toa focusing anode or lens member of a conventional cathode-rayoscilloscope tube.

For twisting the electron beam H, or for correspondingly twisting thepaths of individual electrons issuing from the cathode |2, in case nobeam forming element I5 is provided, a magnetizing member such as apermanent magnet or a pair of pancake coils 2| and 22 is provided,having a magnetic axis lying along or parallel to the axis I4 of thecathode I2 and the anode l3, the coils being on opposite sides of thetube.

For maintaining the shield I5 and the constant velocity grid l9 atsuitable potentials, sources of unidirectional voltage such as batteries23 and 24 may be provided, and a power supply source is provided forenergizing the anode l3 which may take the form of an additional battery25 connected in series with the lower voltagebatteries 23 and 24.

If the apparatus is to be employed for reproducing a grid signal in theanode circuit, a load resistor 26 may be connected in series with theanode |3 to the positive terminal of the power supply 25, and conductors21 and 28 may be connected across the ends of the load resistor 26 forsupplying a signal receiving device represented by a load 29.

For impressing a signal upon the control grid l8, a signal input source3| represented by a rectangle may be provided, or if the apparatus is tobe utilized for producing phase modulation of a carrier, a carriersource or exciter may represent the input source 3|.

If it is desired to provide adjustability of the delay inthe signalapplied to the control,

tors 21 and 28, means are provided for varying H, the electrons arediverted from what would otherwise be a radial path from the cathode |2to the anode l3 and are twisted into the spiral form shown in Fig. 2,the outer portion of the spiral being represented by the referencenumeral IT. The pitch or tightness of the spiral depends upon thestrength of the magnetic field H, and accordingly the point 33 at whichthe beam ll impinges upon the ring cathode or collector I3 is determinedby the strength of the magnetic field H produced by the modulatingvoltage source 32.

For convenience, a single spiral beam H or the spiral path ll of asingle electron has been shown. It is to be understood, however, thatwhere a relatively large output is required it may be preferable toallow the electron emission to take place in all directions radiallyfrom the cathode parallel to the plane of the tube II, that is the planeof the top or bottom surface of the tube The same principle of operationwill take place as before, however. Even though there may be innumerablespiral paths corresponding to the path each such path, will have alinear dimension or length, and consequently an electron transit timedetermined by the strength'of the magnetic field H. If

precision is employed in the construction of the tube and theelectrodes, all of such paths should strike the ring anode l3 atsubstantially the same time, and accordingly a delayed signal appears atthe anode l3 which is a counterpart of the signal applied to theintensity control and 22 up to a. point approaching the cut-oil of platecurrent, and this is accomplished with a minimum number of electrodes;

'In connection with Figs. 1 and 2, an arrangement has been described forproducing modulation or for adjusting signal delay by varying thestrength of the beam twisting magnetic field to vary the length of thebeam or of the spiral electron path; however, the invention is notlimited thereto. The effective length ,of the beam path may also bevaried by distortion of the shape thereof. For example, the plane spiralll of Figs. 1 and 2 may be distorted into conical form so as to liealong the surface of a cone of greater or less angle according to thestrength of a modulating voltage in order to produce variable delay. Anarrangement for accomplishing modulation in this manner is illustratedin Fig.

3. The corresponding elements of Figs. 1 and 3 have been designated bythe same reference numerals, The coils 2| and 22 may be connected to asource of constant direct current 10 as shown or permanent magnets maybe provided grid 3 as it reappears at the output conducconstant field H.

the strength of the beam-twisting magnetic elements 2| and 22. Forexample, the elements 2| and 22 may take the form of' pancake coilsconnected in series to modulating voltage source 32. As a result ofthemagnetic field H produced by the solenoid coils 2| and 22, in adirection normal to the path of the electron beamv in the arrangement Inplace of the annular or ring lector anode |3, a disc shaped anodecollector l3 may be provided. For distorting the shape of the spiralpath H of Figs. 1 and 2, washershaped deflecting electrodes 36 and 31may be provided. The beam deflecting electrodes or deflection plates 36and 31 are mounted near the of Fig. 3forproducingfa shaped col- 2 upperand lower ends of the cathode I2 and are directly connected or coupledto the modulating voltage source 32. In order to minimize defocusingefiect of the anode I3, a second complementary anode 38 may be providedhaving substantially the same shape and size as the anode l3 but locatednear the lower surface instead of the upper surface of the tube II, orvice versa, but preferably the anode 38 is maintained at a po tentialhigher than that of the collector anode 13' by suitable means such as bymeans of a supplementary voltage supply or battery 39 connected betweenthe anode 38 and the positive 7 terminal of the power supply 25 of theanode l3. It will be understood, of course, that iiipreferred, both ofthe anodes l3 and 38 may be connected in the load circuits, that is inseries with the re sistor 26 so that an input of either polarity fromthe modulating voltage vsource 32 will produce a phase modulation in thesame direction in the output signal taken from the conductors 21 and 28.

In the arrangements of Figs. 1 and 3 in which the magnetic field H iscaused to pass parallel to the axis (4 of the tube or envelope H, normalto the radii emanating from the cathode l2, the twisting of the electronpaths into spirals gives rise to a circular component of electriccurrent owing to the moving electrons, which in turn produces a magneticfield which acts parallel to the magnetic field H but in the oppositedirection. However, the electric current efiect of the moving electronsis relatively small and is compensated by the use of a magnetic field Hof adequate strength.

If desired, the beam forming shield l may be modified in constructionand in the arrangement of its aperture IS in such a manner thatelectrons are allowed to issue only at a small point and would travelwithin a single plane, namely the horizontal center plane of the tube Hwere no modulating voltage applied to the deflecting plates 36 and 31.The presence of a small direct voltage between the plates 36 and 31tends to warp the electron beam from a spiral path in such a horizontalplane so as to follow a path of a conical spiral as the result of whichthe end of the conical spiral beam ll strikes the anode I3 at a point33'. A sufilcient voltage to warp the electron beam path into the shaperepresented by the conical spiral is provided by a deflecting circuitbias voltage source such as a battery 4 I.

If the deflecting voltag is increased as the result of a signal appliedby the modulating voltage source 32, the conical spiral I1 is furtherdistorted from a flat plane and follows the surface of a cone of sharperapex angle as represented by a conical spiral path 42 impinging upon thecathode l3 at a point 43. Inasmuch as the radial pitch of the electronbeam is relatively unchanged by the variaton in modulating voltage, thepath of the beam is made shorter as the result of the decreased radius,since the point 43 is closer to the center of the tube and the cathode|2 than the point 33'. Thus, in the arrangement of Fig. 3, variation intransit time effect is accomplished by varying the radius of the splralbeam to vary the length thereof as the result of the warping of the beaminto a cone of sharper apex angle.

In the arrangements thus far described, the electrons would travel inradial paths unless twisted into spiral paths by the transverse magneticfield. However, the invention is not limited thereto, and includesarrangements in which the electrons are twisted from some other normalrectly heated cathode 46, a conventional intensity control grid 41adapted to be coupled to a signal input source represented by terminals3| and a screen grid or focusing electrode 48 held at a suitablepositive potential by means of a voltage source represented as a battery49.

At the opposite end of the tube 44, there is a conventional collectoranode 5| lying in a plane substantially perpendicular to the axis of thetube 44 and connected to an anode voltage source represented as abattery 52 with a load resistor 26 connected in series with the voltagesupply 52.

Where modulation or adjustment of signal dela is to be accomplishedelectrostatically, the magnet 45 may take the form of a tubularpermanent magnet composed of suitable high coercive force magneticmaterial such as aluminum, nickel, cobalt alloy, for example, or it maytake the form of a solenoid or coil of current-conducting wire connectedto a source of constant direct current represented by a battery 53. Whenthe magnet 45 is used in this manner, it serves to lengthen the path ofthe electrons or to increase the transit time of the electron beam 55between the cathode 4'6 and the collector anode 5|. 'lhe electron gun,comprising elements 46, 41 and 48, is preferably :0 arranged as toproduce electron beam deviating slightly from the axis of the tube 44and the magnetic axis of the magnet 45 or the electron gun is arrangedto produce a divergent cone of electron rays in order that the electronstreams will have a component normal to the magnetic axis of the magnet45, whereby twisting action may be produced.

Where the modulation is to be accomplished magnetically, the source ofmagnetizing current 53 is made variable in response to modulation or aseparate source is connected across a current limiting resistor 56 inseries with the constant current source 53 and the solenoid coil 45.Terminals 32' for connection to a modulating voltage source such as thesource 32 in Figs. 1 and 3 or some other source of a delay controlvoltage, may be connected directly to the solenoid coil 45 or may beconnected through an impedance-matching transformer 51.

The tightness of the spiral beam 55, that is the pitch and radius, arevaried by varying the strength of the magnetic field produced by thesolenoid 45 in response to variations in the input signal through theterminals 32. A resultant variation in transit time of the electronsvaries the delay in the signal appearing across the load resistor 26serving as a counter-part of the signal supplied at the intensitycontrol grid 41 through the signal input terminals 3|.

Ii electrostatic delay control or phase control is desired instead ofmagnetic, a pair of velocity control electrodes 58 and 59 may beprovided which are preferably relatively close to the electron gun andto the anode 5 1' respectively in order to exert the maximum controlover electron ve- 76 locity. In this case the impedance matchingtransformer 51 is connected to the electrodes 58 and 58 instead of tothe solenoid coil 45, and a constant current is supplied to the coil 45for producing a relatively long helical-electron beam path 55. Torepresent the change over from one form of modulation to the other, adouble-throw, double-pole switch 6| has been shown having a pair ofblades 62 connected to the impedance matching transformer 51, having onepair of stationary contacts 63 connected across the resistor 56 andhaving two other stationary contacts 64 and 65 connected to the velocitycontrol electrodes 58 and 59 respectively. When the switch blades 62 aremoved from the position illustrated to a right hand position makingconnection with the stationary contacts 64 and 65, modulating ordelay-controlling voltages 180 degrees apart are applied to theelectrodes 58 and 59, but preferably a bias source 66 is provided forpreventing the electrodes 58 and 59 from drawing current. When theelectrodes 58 and 59 are to be utilized, the bias source 66 is connectedto a tap 61 of a secondary winding of the transformer 51 by closing aswitch 68.

It will be understood that the coils 2l--22 in Fig. l and the magneticbeam twisting coil 45 in Fig. 4 may be so shaped as to produce anydesired variation in magnetic field strength along the ordinary electronpath which would exist if the magnetic coils were not present. Forexample in the case of the coil 45 of Fig. 4, the ends of the coil maybe tapered as at 45a so as to cause the magnetic field strength toincrease gradually as the beam 55 enters the magnetic field and to,

cause the magnetic field strength to recede gradually again as the beamleaves the field of the coil 45 in order to cause the beam 55 to enterand leave the helical spiral form gradually.

Preferably suitable means are provided for refocusing and straighteningthe spiral electron beam 55 before it reaches the cathode 5|. Forexample, a refocusing electrode 69 may be provided held at a suitablepotential by a battery H. With the change over switch 6| thrown to theright hand position making contact with the contacts 64 and 65, themodulating voltage source 32 is in effect connected in push-pullunbalanced relation to the velocity control electrodes 58 and 59. Thepermanent magnet or the constant current solenoid magnet 45 serves tosupply a constant twist to the electron beam 55 for a given electronvelocity, and the transit time is then varied by the variation inpotential of the electrodes 58 and 59. The variation in velocity alsohas some efiect on the twist of tightness of the helical-electron path,and accordingly variation in signal delay or phase modulation of thesignal applied at the terminal 3| is produced by variation in voltageapplied at the terminal 32.

Certain embodiments of the invention and certain methods of operationembraced therein have been shown and particularly described for thepurpose of explaining the principle of operation of the invention andshowing its application, but it will be obvious to those skilled in theart that many modifications and variations are possible, and it isintended, therefore, to cover all such modifications and variations asfall within the scope of the invention which is defined in the appendedclaims.

Iclaim:

1. An electron discharge device comprising in combination an emitter forprojecting electrons radially with respect to an axis, an intensitycontrol electrode in front of the emitter, a constant velocity electrodein front of the intensity control electrode, a pair of beam deflectingelectrodes coaxial with respect to said emitter in the form of washersmounted at the ends of the emitter in planes transverse to said axis,and a collector transverse to said axis.

2. An electron discharge device having an axially located emitter forprojecting electrons radially with respect to the axis of said device, acollector anode lying in a plane substantially normal to said axis andnear one end of said emitter, means for setting up a magnetic fieldwithin said device in a direction parallel to said axis, whereby saidelectrons are caused to traverse a spiral path lying along the surfaceof a cone so as to impinge upon said collector anode. and an intensitycontrol electrode coaxially disposed with respect to said emitter andadapted to vary the emission intensity of said emitter in accordancewith a signal applied to said control electrode.

3. An electron discharge device having an axialli located emitter forprojecting electrons radially with respect to the axis of said device, acollector anode lying in a plane substantially normal to said axis andnear one end of said emitter, means for setting up a magnetic fieldwithin said device in a direction parallel to said axis, whereby saidelectrons are caused to traverse a spiral path lying along the surfaceof a cone so as to impinge upon said collector anode, and a pair ofdeflection plates disposed parallel to said collector anode and lying oneither side of the normal path of projected electrons.

4:. A cylindrical electron discharge device having a longitudinal axis,an emitter of radiall projected electrons located in substantialcoincidence with said axisja collector anode concentric with said axisand extending radially outward therefrom near one end of said emitter, apair of defiection plates of substantially washer form also extendingradially outward from said axis, said plates being disposed respectivelynear the ends of said emitter.

5. A device according to claim 4, further comprising a cylindricalelectron-permeable control electrode disposed in coaxial relation withsaid emitter and adapted to vary the flow of electrons between saidemitter and said collector anode.

6. An electron discharge device of generally cylindrical configurationhaving a longitudinal axis and comprising: an emitter of radiallyprojected electrons, said emitter being located in substantialcoincidence with said axis; a collector anode concentric with saidemitter and extending in a plane normal to said emitter and near one endthereof; means for maintaining said collector anode at a positivepotential with respect to said emitter, thereby causing electronsprojected from said emitter to flow toward and impinge upon saidcollector anode; means for producing a magnetic field of predeterminedflux density in a direction parallel to said axis, whereby saidelectrons are caused to traverse a spiral path between said emitter andsaid collector anode; and a pair of deflection plates disposed parallelto said collector anode and lying on either side of the normal path ofprojected electrons.

JOHN W. TILEY.

(References on following page) 9 REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Thomas July 19, 1927 Hull Sept.4, 1928 Steenbeck Dec. 28, 1937 Mendenhall Jan. 18, 1938 Skellett Apr.12, 1938 Han-sell Nov. 29, 1938 Dallenbach June 27, 1939 Llewellyn June27, 1939 Number Number

